1. Technical Field
The present invention relates to a driving technology of a discharge lamp emitting light caused by discharge between the electrodes.
2. Related Art
In the projectors using a Digital Micromirror Device (DMD, a trademark owned by Texas Instruments) as a spatial modulation element, it is performed that the light from a discharge lamp such as a metal halide lamp for emitting white light is temporally divided into colored light beams of red, blue, and green, for example, using a color wheel. In the case of driving the discharge lamp with an alternating-current lamp drive current, if the conversion of the polarity of the lamp drive current is performed outside the blanking period of the color wheel, the brightness of a screen might be varied due to the variation in the light output at the moment of the polarity conversion. In order for solving the problem described above, in JP-A-2003-162001, it is proposed to convert the polarity of the lamp drive current in the blanking period in which a segment boundary in a color filter traverses the light beam.
However, in the case of driving the discharge lamp using the method proposed in JP-A-2003-162001, the temperature distribution inside the discharge lamp becomes stationary, and thus an electrode material might be stacked locally on a shaft of the electrode and so on, thereby growing an acicular crystal of the electrode material. In this case, deterioration of the discharge lamp might develop rapidly due to abnormal discharge from the acicular crystal to the inner wall and so on, thereby shortening the life of the discharge lamp.